The present invention relates to a transmit and receive device for improved data transfer in a multi-carrier system, together with an associated method, and, in particular, to a transmit and receive device together with an associated method for improved data transfer in a wireless OFDM-based multi-carrier system having channels which exhibit a quasi-static behavior.
Conventional digital multi-carrier systems transmit and receive digital signals using a multiplicity of carriers or sub-channels having various frequencies. In this context, a transmitter divides a transmit signal into a multiplicity of components, assigns the components to a specific carrier, encodes each carrier in accordance with its components, and transfers each carrier via one or more transfer channels.
A device and a method for improved data transfer in an OFDM multi-carrier system, in which an adaptive modulation is combined with a multilevel encoding, is disclosed on pages 21.1-21.5 of the document reference “Combining Multilevel Coding and Adaptive Modulation in OFDM Systems” by M. Lampe and H. Rohling, 1st OFDM Workshop, Sep. 21-22, 1999, Hamburg-Harburg, Germany.
In this context, the multilevel encoder includes a demultiplexer for dividing a serial data stream into a multiplicity of parallel data streams, a multiplicity of parallel-arranged encoders and post-connected QAM modulators, and a multiplexer for returning data in a serial data stream. The decoder includes a multiplicity of decoders and demodulators which are arranged in parallel, and a multiplexer for returning the parallel data stream in a serial data stream. By combining this multilevel encoding with the adaptive modulation, it is possible to derive a multi-carrier system with improved data transfer properties and reduced susceptibility to failure.
In accordance with the aforementioned document reference, therefore, a data grouping is partitioned and the so-called “weakest” and “strongest” bits are examined with regard to their error susceptibility, wherein on the basis of the observed properties a more or less strong error correction is applied; for example, in the form of FEC encoding procedures (Forward Error Correction). In order to reduce system complexity, the output signal of a relevant demodulator/decoding level is forwarded to the higher-order demodulator/decoder in the multilevel structure of the decoder. The encoders are the same at each level, and are merely punctured differently.
A method and an arrangement for transferring data are disclosed in EP 0 991 221 A2, in which interference characteristics are specified for a selection of n channels to be used for an audio data transfer. For this, data bits of the audio data are divided into n classes on the basis of their sensitivity to errors which occur, the division being performed in such a way that the classes of bits with the highest error sensitivity are transferred on channels which are the least susceptible to interferences.
In contrast, the present invention addresses the problem of creating a transmit and receive device for improved data transfer in a multi-carrier system, together with an associated method.